Vapor electric converter



June 13, 1939. H. KLEMPERER 2,152,434.

VAPOR ELECTRIC CONVERTER Filed Jan. 13, 1938 N 6 T V Z 4 T /5 g 7 l/ c WITNESSES:

lNVENTOR Haas fflem aeren ATTORNEY Patented June 13, 1939 I 2,162,484 VAPOR ELECTRIC CONVERTER Hans Klemperer,

Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a corporation of Pennsylvania Application January 13, 1938, Serial 6 Claims.

My invention relates to a vapor. electric converter, and more particularly to an excitation system for such converter of the high-voltage type.

In the operation of vapor electric converters,

particularly of the high-voltage type, comprising an anode, a mercury p 001 cathode and an igniter electrode in permanent contact with the cathode,

the excitatio with respect to the n are is frequently advanced in phase main arc in order to keep ionization low during the latter part of the conducting period. It the latter part mercury junction jum provided with such de d at the igniter rodps to an auxiliary anode vices. This movement of the cathode terminal of the main arc occurs because the auxiliary the cathode during ducting period.

anode is more negative than the latter part of the con- Droplets of mercury sputtered during the initiation of the cathode spot often strike the auxiliary anode and the unwan more favorable to the droplets. operating conditi However, an adverse ted are transfer becomes movement of the mercury effect upon the ons of the discharge device is the natural result and considerable damage is caused to the auxiliary ano ation of backfire hazards.

de as well as the cre- According to my invention, the position of the grid-controlled discharge unidirectional current device which supplies to the igniter electrode is changed to prohibit the auxiliary anode from becoming more negative the latter part of the con diately at the transition poin at which the exciting than the cathode during ducting period. Immet, that is. the point current reaches zero, the

excitation arc is extinguished. The main arc,

however, continues to rent is still flowing.

is, between the transiti persist because anode cur- During the interval, that on points of the excitation current and the anode current, negative potential does not how to the auxiliary anode for a unidirectional conductor such as a half-wave rectifier is in the circuit supplying current to both the igniter electrode and the auxiliary electrode.

Without the unidirectional conductor in the new position, a high negative voltage would be applied rapidly t high initial backv curre o the auxiliary anode and a very nt would flow for at least a short interval of time because of the high density of ionized vapor present in the anode region.

It is, therefore, an

object of my invention to prevent the transfer of the cathode spot of the main arc to the auxiliary anode during the latter part of the rectifying period.

Another object of my invention is to accelerate the transfer of the anode side of the auxiliary arc from the igniter rodmercury-junction to the auxiliary anode of such devices.

Another object of my invention is to provide suitable means for reducing damage to the auxiliary anode of vapor discharge devices and the consequent backfire resulting therefrom.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing, in which:

Figure 1 is a vapor electric converter an my invention,

Fig. 2 is an illustration showing an alternative circuit for operating vapor electric converters, and

Fig. 3 is a graphical illustration'showing the phase relationship of the working currents according to my invention.

The converter 3 according to Figure l of my invention comprises a suitable evacuated container 5 having an anode I and a mercury pool cathode 9 disposed in the bottom thereof. The converter 3 supplies unidirectional current to a load device 4 from a source 6 of alternating current. An auxiliary anode H is interposed between the main anode I and the cathode 9 to control the rectifying are being maintained in the converter 3. An igniter electrode l3, preferably of some high resistance material, is mounted to be in permanent contact with the cathode 9. The ignition electrode I3 and the auxiliary anode I I are electrically connected at point M. A unidirectional conductor I5, such as a half wave rectifier, is placed between a source of suitable alternating current potential such as a transformer. l1 and the auxiliary electrodes H and I3. Between the transformer l1 and the unidirectional conductor IS, a suitable resistor I9 is placed to limit the current supplied to the auxiliary anode II which is preferably a thin circular disk of some suitable metal. Likewise, a resistor 2| is placed in series with the igniter electrode l3 to facilitate the arc transfer from the igniter rod-mercury junction to the auxiliary anode l l. According to my invention it is essential to shift the pha the auxiliary electrodes H and I3 with respect to the anode current. I have illustrated a convenient method for producing this phase shift by a suitable phase shifter 23.

According toiFig. 2 of my invention,

d circuits embodying the only se of the current supplied to control the excitation current of one of the windings 28. A leakage path 35 is customarily provided between the primary windings 28 and 29, such as is used in connection with the transformer 25 utilizing opposed alternating current windings 28 and 29. By such an arrangement of a highly saturable core 31, grid control of the unidirectional conductor l5 or grid-controlled rectifier is unnecessary.

Alternating current is supplied from the transformer l1 and the unidirectional device I 5 permits current to fiow to the auxiliary electrodes H and I3 only during conducting half cycles, that is, when the anode 1 is maintained positive with respect to the cathode 3. To maintain ionization low during the latter part of the conrent supplied to the auxiliary electrodes H and I3 and B the current supplied to the main anode 1.

The formation of a tiny arc occurs between the igniter electrode-mercury junction when the potential gradient in the igniter rod l3 reaches or exceeds a certain critical value. Potential gradient is established by passing a current to the igniter electrode 13 from some suitable source such as a transformer H. The lower terminal of this arc, or better known as the cathode spot, moves away from the igniter rod l3 along the surface of the mercury cathode 9. On the other hand, the upper terminal of this are travels up- 9 and the main anode 7.

Upon reaching the zero or transition point, represented by letter C in Fig. 3, the excitation cathode 9 and the auxiliary anode H is extinuished while the are between the cathode 9 and the main anode I continues to persist until the transition point, represented by letter D, of the main anode current is reached. During this time, that is, between points and D, the cathode spot is prevented from jumping to the auxiliary anode ll because the current is blocked during the inverse hall cycle by a unidirectional current-transmitting device 15. This is shown as a three-element thermionic discharge tube, but may alternately be any equivalent device capable of passing current only when the mercury pool 9 is at a negative potential with respect to the main anode I. It may be desirable to accelerate the transfer of the are between the cathode 9 and the auxiliary anode II. A suitable resistor 2| is provided for this purpose, so that when current is being supplied to the igniter electrode l3, a voltage drop across the resistor 2| hastens the arc transferring process between the auxiliary electrodes H and [3.

Grid control of the thermionic discharge tube may be eliminated by using an inductive deg transformer 25 capable ages having peak wave fronts. nt flows through the e l only for a short period conducting half cycle. illustration, I have shown a t of my invention. However, to those skilled in the art that fications can be made therein from the true spirit of my inope of the appended claims.

e such as a peakin of generating volt By this arrangem unidirectional devic of time during the For purposes of specific embodimen it will be apparent changes and modi without departing vention and the so I claim as my in 1. A vapor electric c rectifying arc is ex said auxiliary are 3. A vapor ele current for initiating a cathode spot at the junction of said igniter and one of said main electrodes in contact therewith, another source of current for maintaining a rectifying are between said main electrodes, means for displacing said current sources in phase relationship, said dephasing means including a peaking transformer for generating impulses of steep wave fronts and a unidirectional device in series with said transformer whereby the alternate impulses are impressed on said igniter and said auxiliary electrode, said unidirectional device serving to prevent the cathode terminal of said rectifying are from transferring to said auxiliary electrode at the transition point of said igniter current.

6. In combination with a vapor electric converter comprising a plurality of main electrodes,

an igniter electrode in contact with one of said main electrodes and an auxiliary electrode between said main electrodes, said igniter electrode and said auxiliary electrode being electrically connected, means for applying positive potential to said igniter electrode before application of like potential to one of said main electrodes, said supply means for said igniter electrode including a peaking transformer for generation of impulses having steep wave fronts, and means connected in series with said electrically joined electrodes for rendering said joined electrodes inoperative during inverse potential.

HANS KLEMPERER. 

